8 mpg City, no mods except tires...something's gotta be off

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LCbruiser2000

LCbruiser2000

10 Year
Joined
Jun 29, 2011
Threads
17
Messages
205
been doing good upkeep on the truck but i've noticed a bad drop in mileage (and a creaking rear noise which still can't be figured out) after intstalling the 285/75/16

that's the only mod and i'm getting under 100 miles at half a tank of gas....

i know this truck is a thirsty beast, but this is a bit off, no??

searched threads and i saw MAF cleaning/throttle body clean.
i'm only at 63,000 miles and have done everything to boot so far.
any other suggestions??

thanks in advance
 
Trunk Monkey said:
Tune up - plugs, air filter, check your tire pressure, and don't have a heavy foot.
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my foots not that heavy...i drive slower as i get older
40psi all the way around
plugs were changed
and air filter was changed about 1000 miles ago....

still not good is it?
 
I have a 99 Land Cruiser and just installed 285/75/16 BFG's A/T tires. I have no other mods. Based on a few weeks of driving, I get 15.1 miles hwy and 13-14 city. I have 83K miles and just replaced my spark plugs. It sounds like something is wrong with your Cruiser.
 
SanDiegoCruiser said:
I have a 99 Land Cruiser and just installed 285/75/16 BFG's A/T tires. I have no other mods. Based on a few weeks of driving, I get 15.1 miles hwy and 13-14 city. I have 83K miles and just replaced my spark plugs. It sounds like something is wrong with your Cruiser.
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i'll have to drop it at SDTrux next time I'm down that way.
Have him do Trunks "deeper inspection"
ugh

I really hope there isn't something wrong. The outside is so purdy, why can't the innards match:crybaby:
 
i get about 9 in the city 13.5-14.5 on the highway. Mine LX is tuned up and very well maintained
 
I'm at 11 city, 13 highway, which used to worry me.

But from all my reading on this forum about this topic, anything in the range of 8-12 city and 11-17 highway is considered fairly normal...
 
In L.A., CA (probably heavier traffic than most "city" driving and crappy CA blend gas), I get between 9 and 10.5 MPG in the city (on regular/87 gas). Computer always tells me a little better than a calculator. I have not adjusted speedo for my slightly bigger tires 275/65/18's (otherwise it's stock). For what it's worth, it seems (no science) that, with the bigger tires, I get slightly better (like .5 MPG) with the "power" button pushed in on my transmission. I'm going to try a couple of tanks of supreme (91) gas to see if that makes a noticeable difference.
 
One thing to remember - since you just put bigger tires on your Cruiser, your speedometer is going to be off. If you are using this to determine your millage, it will be lower than what it really is. I use my GPS's trip meter to monitor how many miles I drive between tanks.
 
LA traffic sucks....when I inch along for an hour back and forth I want to shoot myself...but I *never* look at a prius or any other of those little eco-cars and wish I was in them... I'd rather be in a tank and deal with the crappy mpg.

not complaining, just making sure nothings wrong cause if it is, i wanna take care of it before it's an issue
i love my baby bruiser!
 
are you accounting for any speedo correction required with the larger tires?
 
SanDiegoCruiser said:
One thing to remember - since you just put bigger tires on your Cruiser, your speedometer is going to be off. If you are using this to determine your millage, it will be lower than what it really is. I use my GPS's trip meter to monitor how many miles I drive between tanks.
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Good point, it's about a 3% difference. So 100 miles on the odometer was really 103 miles. Not huge, but worth noting if you're really measuring MPG's.
 
nakman said:
Good point, it's about a 3% difference. So 100 miles on the odometer was really 103 miles. Not huge, but worth noting if you're really measuring MPG's.
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that's true i forgot to incorporate that. i'm not anal about #'s, i just do it to make sure things are running the way they are supposed to be running.

i just don't think at no mods except tires (and 3rd rows In) i can't even manage to get 250 miles to a tank....

i'm a whopping 155pounds and usually driving solo :/
 
I had the same problem. Ended up that the o2 sensor was bad. Changed that out and mileage went back up.
 
I am re-geared and on 35s. Whenever I check odometer vs GPS, I am usually within a 100 feet on a 20 mile trip. I have replaced O2 sensors, cleaned throttle body, cleaned mass air flow sensor, tested with and without air filter, gotten the 90k PM (fuel filter and some other odds and ends that should help with MPGs), tried 87, 89, 93 grades of gas from all major companies, ran with/without roof rack, full vs. empty vehicle, religiously perform PM on driveshafts, tried running anywhere from 33-55 PSI in my tires, tested 33" and 35" tires, tested with A/C on/off, tested in warm and cold, and probably tried about 10 other things that I can't think of off the top of my head. I drive slow and am delicate with the throttle. This is the same MPG I got with my white 99. The only thing I haven't tried is new spark plugs (I actually did replace the spark plugs on my 99) or a new ECU. I'd like to see the people who say they get 15 MPG w/ modded rigs in the city do the following as a test:

1. Fill up
2. Drive 220 miles in city
3. Fill up again and report how much fuel it took

After that we can work out tires sizes, re-gears, weight and what-not.
 
Last edited:
pfran42 said:
I am re-geared and on 35s. Whenever I check odometer vs GPS, I am usually within a 100 feet on a 20 mile trip. I have replaced O2 sensors, cleaned throttle body, cleaned mass air flow sensor, tested with and without air filter, gotten the 90k PM (fuel filter and some other odds and ends that should help with MPGs), tried 87, 89, 93 grades of gas from all major companies, ran with/without roof rack, full vs. empty vehicle, religiously perform PM on driveshafts, tried running anywhere from 33-55 PSI in my tires, tested 33" and 35" tires, tested with A/C on/off, tested in warm and cold, and probably tried about 10 other things that I can't think of off the top of my head. I drive slow and am delicate with the throttle. This is the same MPG I got with my white 99. The only thing I haven't tried is new spark plugs (I actually did replace the spark plugs on my 99) or a new ECU. I'd like to see the people who say they get 15 MGP in the city do the following as a test:

1. Fill up
2. Drive 220 miles in city
3. Fill up again and report how much fuel it took

After that we can work out tires sizes, re-gears, weight and what-not.
Click to expand...

holy jesus mary you've done a lot of tests!
sucks i can't get a straight 220 in the city. i could probably do about half that.
but by the time i get a full tank in, it's a combo of city/hwy

will that still work on your test?

i called my trusty mechanic and he had no answers for me, plus i can't take it to him til december anyway, so i'm basically on my own til then
 
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